The puzzle is a 3D paint-by-number puzzle, creating a 10x10x10 cube of
blocks. Look at each face of the cube head-on, and only consider the
first half ("half smile") of the 10 layers (so that's 5 layers ["five
blocks away"]). For each direction in x, y, and z, this gives a letter
facing each way ("Janus", "sandwich board").